These questions are sufficient to show that realism is a very serious issue for theology, but theology has its counter-questions to ask, says Barth. The most fundamental of them is whether theological realism takes into consideration the fact that the grace of God contradicts us. It is on this ground, that grace opposes sinful man, and objects to his sin, on the ground of a contradiction between the revelation of God and the activity of man, that we can distinguish the objectively given reality of God-in-his-Word from our own subjective states, but also from the other objectivities we encounter in our experience of the world around us. Classical theological realism operates with a basic, naïve conviction that we are able to read knowledge of God off what is given to us in our experience because we stand in relation to him by virtue of the fact that we exist. But when we actually know God through his Word a very different conviction arises, for here a light shines into our darkness, and something quite new is revealed to us which does not just reinforce what we already know, but rather calls it in question. This new knowledge comes as grace that forgives and judges us, and which we cannot just assimilate into our existence, for it lays claim upon us and summons us to encounter the independent objective reality of the living God, the Creator and Redeemer.
Concretely this is what happens when we meet God in Jesus Christ and know him as Lord by the power of the Spirit. It is in that encounter that we learn that the objective act of God upon us in the freedom of his Spirit is to be distinguished from our inward subjective conditions, and that the God who meets us face to face in Jesus Christ is not just nature, or history, or the actuality of our existence with which we are bound up and from which we cannot escape, but a living God who really comes to us and acts upon us in the midst of all the other actualities and objectivities of our historical and natural existence. In other words, here we are faced with a deeper and more fundamental objectivity, with the ultimate objectivity of the Lord God, and therefore it is here that theology is both basically realist and yet to be distinguished from every form of philosophical realism.
In the second place, however, theology must face the critical question posed by philosophy as to the adequacy of its thought to its proper object—that is the question of truth, which gives rise to the problem of idealism. This is the question that seeks to penetrate behind the given, the finite, the objectifiable, and behind all actuality to its ultimate validation or presupposition. Idealist thinking, says Barth, has a negative critical side, and a positive speculative side. On the one hand, it questions the basic assumption of realism, inquires into the reliability of the correlation between subject and object, and reveals the limits within which realist thinking can operate. It refracts or breaks the movement of realist thinking, and so makes it point beyond itself to its object. This critical operation both reminds us of the inadequacy of our human thought-forms and calls for a greater and more exacting adequacy. But idealist thinking has another speculative side, in which it poses as the criterion of reality and exalts itself over against pure being. Idealism of this sort is the self-reflection of man’s spirit over against nature, the discovery of the creative reason as the source of the correlation between subject and object.
Idealist thinking, at least in its critical form, is a necessary element in theological thinking, for whenever there is serious thinking about God, a distinction must be drawn between the givenness of God and the givenness of all other being. That is the relevance of mysticism or of the via negativa even for the classical realism of the Middle Ages, for a realist theology requires a powerful element of idealism in order to be genuinely realist. Is the idealist distinction between ‘the given’ and ‘the not-given’ not necessary for a proper understanding of the difference between divine revelation and all other knowledge that claims to be knowledge of God? And just because in theology we are engaged in human thinking about God, and with the articulation of knowledge of God in human thought-forms, must we not ask the question as to the adequacy of these thought-forms to God? Does not idealist thinking teach us that the best of our thought-forms can only point beyond to the ultimate reality of God which cannot be captured and formulated within the four corners of our human concepts and propositions? That is why idealism is the necessary antidote to all thorough-going realism, for it prevents realist thinking from confounding God with the actualities of our existence, with nature, or history, or necessity.
But may not idealism itself prove the greater danger, especially when it refuses to rest content with the humble critical refraction of our thinking, but insists on making out of the reason itself the criterion of truth, and so exalting itself above God? Is not the danger of idealist thinking in theology that it may lead to the substitution of ideology for genuine theology, a system of self-sufficient truth for an activity of human thinking that points away from itself to the object of its knowledge as the sole source and ground of truth, and as the Truth of God? Hence here, too, theology has its counter-questions to ask of idealist thinking in theology.
The fundamental question we have to ask is directed to the idealist question posed not from the side of the object but from the side of the subject. Does the attempt to reach out beyond all the dialectical antitheses and antinomies of human thought to an ultimate synthesis ever really get outside the circle of its own subjectivity, ever really get beyond the human subject from which it started? Does it not, after all, confound God with the conclusion to its own argument or with the goal of its own upward movement of thought? Is it not in the end projecting its own thought into the infinite and calling it God?
The fundamental question theology must put to the idealist is whether he is ready to let God be God, and therefore ready to let knowledge of God be grounded in God’s own self-revelation, and the establishment of the truth of that knowledge be God’s act and not man’s. In other words, the question which theology must pose over against idealism is the question directed from justification by the grace of God alone to every Pelagian or semi-Pelagian attempt on the part of the human reason to be able to acquire knowledge of God or at least to be able to test and establish the truth of revelation on its own ground. If God is really God, then knowledge of him must be by way of humble obedience, by way of listening to him and serving his Word, and yielding our minds to the direction of his Truth. God is God, and not our idea of God, and therefore all our ideas of him have to be called in question by the very critical question from which idealist thinking takes its rise. And yet here, theology must beware lest it is after all engaging not in theological thinking, but in some form of philosophical idealism itself, for the critical question theology directs does not arise out of any independent rational movement of its own, but is forced upon it by the object of its knowledge, and by the nature of the objectivity of the object, the nature of God who gives himself to us in sheer grace and remains sovereignly free in his transcendent Lordship over all our thoughts of him and over all our formulations of the understanding he gives us of himself in his Word.
The problems posed by philosophical realism and idealism must be taken seriously by theology, but they are questions that theology must learn to raise in its own way and in the closest relation to its own proper object. But the discussion with philosophy shows theology that it must take seriously both poles of its thinking, truth and actuality, thought and being, the knowing subject and the object known. Theology learns that there can be a one-sided realist theology which is tempted to confound God with nature, and there can be a one-sided idealist theology which is tempted to confound God with the reason. Inevitably, therefore, the dialectic between these two counter-movements will throw up the correctives from either side which the other side needs. In such a situation it is possible that a theology may be more realist in orientation and still be theology and another may be more idealist in orientation and still be theology—rather than some species of philosophy or ideology.
But a good theology cannot rest content with that sort of dialectic; rather has it to think more concretely out of the depths of its own concern, and engage in a more material mode of thinking of the tensions between the knowing subject and its given object that is governed by the nature of its subject-matter.